1. Field of the Invention
This invention relates to a chemical supply system adapted to discharge a predetermined quantity of a solution such as a chemical, and concerned with a chemical supply system suitable for use in coating a photo resist solution onto an outer surface of a semiconductor wafer, for example.
2. Related Art Statement
In manufacturing processes of various technical fields including a technique of manufacturing semiconductor wafers, a technique of manufacturing liquid crystal bases, a technique of manufacturing magnetic disks, a technique of manufacturing multilayer wiring bases and so forth, there have been used chemicals such as a photo resist solution, Spinion glass solution, a polyimide resin solution, pure water, a developing solution, an etching agent and an organic solvent.
For example, when the photo resist solution is coated onto the outer surface of the semiconductor wafer, the photo resist solution is dropped onto the outer surface of the semiconductor wafer in a state where the semiconductor wafer is rotated in a horizontal plane. As a chemical supply system used for coating the above-described photo resist solution, there has been used one, in which a pumping mechanism is obtained through an elastically deformable tube and bellows.
As the chemical supply system, in which the pumping mechanism is obtained through the bellows, such ones as shown in FIG. 8 have been developed for example. FIG. 8(A) shows a chemical supply system, in which a pump chamber 51 is formed at the outside of the bellows 50, and which is adapted to guide the chemical in a chemical tank 53 into the pump chamber 51 and to discharge the chemical from a coating nozzle 54 through expansion or shrinkage of the bellows 50 by a driving rod 52 assembled into the bellows 50. Furthermore, FIG. 8(B) shows a chemical supply system, in which an expandable or shrinkable flexible tube 55 is provided in a portion of a flowpath for connecting the chemical tank 53 to the coating nozzle 54, and a pressurizing chamber 56 provided in a tubular member disposed at the outside of the flexible tube 55 is connected to the pump chamber 51 disposed at the outside of the bellows 50.
In Patent laid-open No.29207/1993, there is disclosed a chemical supply system for coating the chemical by use of the flexible tube or flexible film similarly to FIG. 8 (B). In this system, the chemical is guided into the flexible film and incompressible fluid is subjected to the pumping operation by an actuator at the outside of the flexible film.
However, in the case where the bellows-type actuator is disposed at a position spaced apart from the flexible film and the incompressible fluid is supplied from the actuator to the exterior of the flexible film as described in this gazette, the system as a whole becomes large in size. Moreover, the system becomes complicated in construction, it is difficult to easily exchange parts positioned in portions being in contact with the chemical, it is uneasy to perform filling the incompressible fluid into the system, and it is uneasy to carry out the manufacturing work. Furthermore, it is difficult to control the incompressible fluid, and there may occur such a problem that, when leakage of the incompressible fluid occurs, the leakage cannot be easily detected and the system lacks the reliability.
Furthermore, in the case where the pumping operation of the chemical is directly performed by the bellows, the flow of the chemical does not occur at the rear end of the bellows 50, and moreover, since the outer surface of the bellows 50 is irregular as being concave or convex, there is a possibility of the chemical being stagnant in the pump chamber, so that the chemical may show a change in properties due to the stagnancy, to thereby serve as a cause of raising dust during the coating.